Laser-radiation from diode-laser arrays is frequently used for tasks such as heating material for surface treatment, and optically pumping solid-state lasers. The diode-laser array may be a one-dimensional (linear) array or a two-dimensional array. Typically, a one-dimensional array of diode-lasers is made by forming a plurality of diode-lasers (emitters) in a common substrate. This is commonly referred to as a diode-laser bar. A plurality of such bars can be stacked to form a two-dimensional diode-laser array.
Typically, a diode-laser bar for providing laser-radiation having a wavelength of between about 800 and 1000 nanometers (nm) is about 10 millimeters (mm) long, about 1 mm wide and may include between about 2 and 50 individual emitters, spaced-apart along the diode-laser bar. The emitters have a rectangular emitting-aperture about 1 micrometer (μm) high and between about 50 μm and 100 μm wide. The emitters are arranged with their emitting-apertures aligned in the width direction of the emitters, which is in the length direction of the diode-laser bar. Accordingly, the emitters in a diode-laser bar may be spaced apart by only a few micrometers in the length direction of a bar.
When diode-laser bars are stacked to form a two-dimensional array of diode-lasers, spacing of corresponding diode-lasers in adjacent bars is determined by the thickness of the bar and any cooling device associated with the bar. This results in a vertical spacing of emitters which may be no less than about a millimeter. It would be useful to provide optical apparatus that could provide the effect of more closely vertically spaced emitters in a two dimensional array of diode-lasers.